1. Field of the Invention
This invention generally relates to a linear motion guide unit, and, in particular, to an indefinite linear motion guide unit suitable for use in guiding a linear motion over an extended distance. The present invention is particularly suited for use as a component of a driving unit in various precision processing machines, testing equipment or the like.
2. Description of the Prior Art
An indefinite linear motion guide unit having four endless circulating paths is well known as disclosed in the Japanese Patent Laid-open Pub. No. Hei 1-175564. The linear motion guide unit disclosed in this publication is illustrated in FIGS. 5 and 6 herein and it generally includes a rail, a slider and a plurality of rolling members interposed between the rail and the slider. The rail includes on each side a pair of upper and lower inner guide surfaces which are inclined at opposite directions. The slider includes a slider main body H which in turn includes a horizontal section H and a pair of vertical sections each depending from the horizontal section H and each defined by combining three blocks E, F and G together by a bolt. The vertical section is fixedly attached to the horizontal section H by means of a bolt I.
In the vertical section defined by a combination of the three blocks E, F and G, a pair of endless circulating paths C and D are formed, and the paths C and D are filled with a plurality of rollers A and B, respectively. Each of the endless circulating paths C and D has a load path section, which defines an outer guide surface opposite to a corresponding one of the inner guide surfaces of the rail, a return path section, which runs in parallel with the load path section, and a pair of curved connecting path sections connecting the corresponding ends of the load and return path sections, as well known in the art.
In the above-described structure, since a plurality of mounting bolts I are used along each side of the horizontal section of the slider main body H, difficulty is encountered in mounting a slider table on the slider main body H. Under the circumstances, in order to allow to mount a slider table on top, there must be provided a slider main body J having an extended width W1 as shown in FIG. 6. In the structure shown in FIG. 6, a mounting hole K may be provided in the slider main body J as offset in position from the endless circulating paths C and D, so that a slider table may be fixedly mounted on the slider main body J. In this case, however, the center-to-center distance W2 between the two corresponding mounting holes K in the slider main body J also becomes larger. As a result, a slider table to be mounted on this slider main body J necessarily becomes larger. Accordingly, the overall size of the slider main unit J and thus that of the guide unit tends to become larger.
As shown in FIG. 6, as well known in the art, an end block (not shown) is fixedly attached to each end of the slider main body J and an end seal L is fixedly attached to each of the end blocks by means of bolts M.